Vapor generating installation with multiple platen radiant superheater



May 2, 1961 Original Filed v P. H. KOCH ET AL VAPOR GENERATINGINSTALLATION WITH MULTIPLE PLATEN RADIANT SUPERHEATER Dec. 6, 1950 5Sheets-Sheet l lNVENToRS Paul r /Koc/z ATTO R N EY 4 FIG.1 36

May 2, 1961 PLATEN RADIANT SUPERHEATER 1950 5 Sheets-Sheet 2 OriginalFiled Dec. 6.

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INVENTORS Pazz/ H Koch BY flrfkzgr E/Payzwfi TTORNEY 5 Sheets-Sheet 3May 2, 1961 P. H. KOCH ETAL VAPOR GENERATING INSTALLATION WITH MULTIPLEPLATEN RADIANT SUPERHEATER Original Filed Dec. 6, 1950 E N a 6 T W 08800 8 WI liilibll{ll-{LI}--.i...

XXIXKXIIXXIIIXQKXIXyIlIXXIXXXXXXXIXXXXIXIXXXXIIXXX'III INVENTORS Pau/.79. 1520/1 fl flzwE fla nor ATTORNEY m oooooo Eif:i-Illlillllllllilli-..

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May 2, 1961 P. H. KOCH ET AL 2,982,268 VAPOR GENERATING INSTALLATIONWITH MULTIPLE PLATEN RADIANT SUPERHEATER Original Filed Dec. 6, 1950 5Sheets-Sheet 5 INVENTORS Paul H.Koch

BY Ar rhur E. Raynor a'bM' ATTORNEY U t tates aenr I 2,982,268 VAPORGENERATING INSTALLATION WITH MULTIPLE PLATEN R AD I A N T SUPER- HEATERPaul H. Koch, Bernardsville, N.J., and Arthur E. Raynor, RockvilleCentre, N.Y., assignors to The Bahcock & Wilcox Company, New York, N.Y.,a corporation of New Jersey Original application Dec. 6, 1950, Ser. No.199,480,

now PatentNo. 2,811,955, dated Nov. 5, 1957. Di-' vided and thisapplication Oct. 2, 1957, Ser. No. 687,719

12 Claims- (Cl. 122-480) This invention relates to steam generating andsuperheating installations, and it is more particularly concerned withsuch installations in which steam is generated and superheated at hightemperatures and pressures in tubes exposed to heat of a furnace burninga slag forming fuel and operating 'athigh gas temperatures.

More particularly theinvention is concerned with steam generating andsuperheating installations such as above indicated, fired by the burningof a granular slag forming fuel such as coal, in a cyclone furnace, andhaving platensof radiant superheater tubes exposed directly tofurnacegases in a part of a secondary furnace chamber receiving products ofcombustionfrom the cyclone furnace.

Inthe rapid progress of modernsteam generation and steam superheating,greater and greater efficiencies have been attained by operation athigher and higher temperatures and pressures, and with this attainmentof increasingly higher'efiiciencies, increasingly greater portions ofthe ,total heat released has been absorbed by the installationcomponents other than'the furnace. Such components include the steamsuperheater and reheater. With the concomitant decrease of total heatabsorbed by the furnace of such installations, the products ofcombustion passing from the furnace have attained increasingly highertemperatures, and with the insistent demand for higher efiiciencieshigher gas temperatures have been necessary to attain the desired finalsteam temperatures. These temperatures have been within the range inwhich slag particles are carried with the gas into the superheatingzone, in installations burning slag forming fuels. This condition, andthe important consideration of minimizing draft losses have created ademand for an optimum superheater which would attain the higher finalsteam temperature with a minimum. of slagging and with a minimum draftloss.

This invention meets the indicated demands by pro-' LCQ radiantsuperheaters. Furthermore, the radiant superheater of the presentinvention is so constructed and arranged that it does not involve anysuch maintenance viding a superheater including radiant tube platensdirectly exposed to'the higher temperature combustion products within ahigh temperature furnace chamber. The tubes are arranged in platensextending generally in the direction of gas flow and are constructed anddisposed in the furnace so as to minimize the difficulties resultingfrom the expansion and contraction of the tubes, considering the hightemperatures of their normaloperation.

The superheater tube platens of the invention are so constructed andarranged to provide the necessary superheat capacity without incurringthe difficulties which would result if attempts were made to attain suchC3:

pacity by using wall tube radiant superheaters or similar furnaceboundary superheaters in which the tubes are disposed along suchboundaries. With the radiant superheater of the present invention, thesize of the furnace is reduced, as compared to a furnace which would benecessary if all of the radiant superheater capacity were attained' y he of 'wall ube q fu n c bo nda y difficulties as those involved inmaintaining the furnace boundary integrity of a wall tube or furnaceboundary radiant superheater. The superheater platens of the presentinvention are so arranged, constructed, and maintained that theexpansion and contraction of the superheater tubes do not materiallychange their operative arrangement.

In the specific constructioncovered by the present invention, theradiant superheater tubes are arranged with a plurality of platens at,the top of a high temperature furnace-chamber with the tubes of theplatens extending upwardly from headers at one side of the chamber. Thetubes extend at an upward inclination across the chamber and thenvertically upward in platen formation to posi tions in front of the gasoutlet of the furnace chamber.

. This arrangement with the headers mounted at the lower ends of thetubes of the various superheater platens, pro.- vides asuperheater whichis readily drainable so as to eliminate difiiculties which mightotherwise be caused in the starting up of the installation. Thisapplication is a division of our application Serial No. 199,480, filedDecember 6, 1950,, now Patent No. 2,811,955. The invention is describedherein with reference to an illustrative installation shown in theaccompanying drawings 7 In'the drawings: T Fig. 1 is a vertical sectionthrough the illustrative installa tion; V v

Fig, 2 is a horizontal section on the section line 2-4-2 of Fig. 1,looking in the direction of the arrows;

Fig. 3 is a horizontal section on the line 33 of Fig. 1; Fig 4 isa-vertical section generally on the line 4-4 of Fig. 2, but with a partbroken away to show a partial section on the line 4A4A of Fig. 2;

Fig. 5 is a fragmentary elevation showing the manner of supporting thesuperheater tubes upon the roof tubes; and

Fig, 6 is a section in perspective of the convection vapor heating gaspass of the present invention. a

The drawings indicate a high capacity steam generat: ing andsuperheating installation operating at a steam pressure of the order of875 p.s.i., and at a capacity of 575,000 lbs. per hour. The installationinvolves a steam superheater and reheater each delivering steam at 1000F.

The illustrative installation involves fuel burning means including acyclone furnace generally indicated at 10 in Fig. 1, This furnace ischaracterized by high combustion efficiency and a recovery of a highpercentage (90-95%) of the recoverable portion of the fuel ash in theformation of molten slag. The cyclone furnace and its associatedcomponents are constructed and arranged in a manner similar to thatindicated in the US. patent to Bailey et al. 2,357,301, September 5,1944. In the operation of the furnace, crushed coal and a supply ofpreheated primary air under superatmospheric pressure are deliveredtangentially to the cyclone furnace at the inlet 12; This introductionof primary air and coal to the furnace takes place at a velocity highenough to cause the coal particles to be thrown toward the cylindricalwall of the cyclone which is formed by fluid cooled studded tubescovered on their inner sides by high temperature refractory material.High temperature secondsts c m ust on n he rsl ne na is high o h to meltthe ash into liquid slag which clings to the wall of the furnace. Theparticles of incoming coal are trapped in this surface layer of moltenash, and the scrubbing action of the high velocity of combustion airover these coal particles results in effective combustion at high fuelburning rates.

The combustion gases with slag particles therein exit from each primarycyclone furnace chamber 16 through its outlet 18 in a turbulentcondition, and slag formed and accumulated in this cyclone chamber 16passes through the slag opening 20 formed by outward bends .in some ofthe fluid cooled tubes defining the rear wall "22 of the primary chamberof the cyclone. Slag flowing through the opening 20 drops to a slagcollecting bottom 23 of the secondary cyclone chamber 24, from which itpasses through an opening 26 and drops into a body of water within theslag pit or tank 32.

The upper and rearward wall of the secondary chamber of the cyclonefurnace is defined by steam generating tubes 28 connected into the fluidcirculation system of the installation., Parts of these tubes, withtheir covering of refractory on their furnace sides form the reflectingarch 30. Below this arch, the steam generating tubes are bent to formthe transversely placed platens of a slag screen 34, disposed at anangle of approximately 45 to the horizontal as indicated in thedrawings. These platen forming tubes extend downwardly and have theirlower endsdirectly connected to the submerged lower drum 36. Above thereflecting arch 30, these tubes extend vertically from the top of theinclined boundary surface 38. They extend along the furnace chamber wall40 to positions near the top of the installation. Some of these tubeshave roof sections 42 associated with heat resistant material to formthe roof of the radiant heat absorption furnace chamber 44 and thedownward gas pass 46. Others of the tubes disposed along the wall 40extend above the roof of the furnace chamber 44, and then horizontallythrough their circulator sections 50 and 52 to direct connections withthe steam and water separating drum 54. The roof tubes similarly havetheir upper ends 56 and 58 directly connected with the steam and watermixture space of the drum 54.

Gaseous combustion products with their suspended ash particles fiow fromthe secondary chamber of the a cyclone furnace through an outlet beneaththe reflect-- ing arch 30, and between the tube platens 34 into thelower part of the furnace chamber 44. They pass upwardly through thelatter and between widely spaced platens of contiguous radiantsuperheater tubes distributed across the furnace chamber 44. They thenturn to the right and flow horizontally into' the equalizing chamber atthe top of the downpass 46 and over the components of tubes constitutinga reheater and a primary superheater disposed in the gas pass.

The remaining walls of the furnace chamber 44 are defined by steamgenerating tubes having their lower ends appropriately connected to thesubmerged drum 36, and their upper ends connected to the steam and waterdrum 54. The side walls are defined by steam generating tubes 59 (Fig.2) directly connected at their lower ends to transverse headers, such asthe header 60 at the lower part of Fig. 1, this header beingappropriately in communication with the submerged drum 36 by suitabletubular connectors. The upper ends of the side wall tubes are connectedwith the horizontally disposed and diaphragrned headers such as 62directly to the drum 54 by circulators 64.

At the upper part of the installation, as shown in Fig. 2, the upperparts of some of the tubes 59 are arranged in two rows so that they maybe covered with the intervening refractory material 61 to reduce heatabsorption by the tubes and thereby maintain high temperatures of thefurnace gases at the positions of the reheater 100 and the primarysuperheater. In Fig. 2, the two rows of ugper parts of these tubes 59are indicated at 59' and 5 The installation is generally rectangular inhorizontal section as indicated in Fig. 2, having the front wall 40, theside walls 66 and 68, and the rear wall 70. The latter includes steamgenerating wall tubes 72 connecting the intermediate transverse header74 directly to the drum 54. Above this header the tubes 72 are coveredwith refractory material 73 to further promote high gas temperatures.Immediately beneath the header 74 the wall tubes 76 extend in spacedrelationship across the gas outlet 78 of the downpass 46. The flow ofgas through the reheater part of this outlet is controlled by aplurality of dampers 80. The tubes 76 extend downwardly below the gasoutlet 78, and along the wall to direct connection with the drum 36. Thewall 70 includes the heat insulating material disposed externally of thetubes 76 as well as the refractory material 73 disposed on the gas sidesof the tubes 72.

Other steam generating tubes have their lower ends 82 and 84 directlyconnected to the drum 36, and their inclined sections 86 and 88associated with their refractory material 90 to form an inclined wallextending downwardly toward the fioor 23 of the secondary chamber of thecyclone furnace. Above this inclined section, these tubes have theupright portions 92 extending along the lower part of the wall 70. Nextabove these are the inclined sections 94 associated with other tubesections and refractory material to form an inclined base for thedownward gas pass 46. Beyond this base these tubes are joined bybifurcations 96 to upright portions 98 disposed along the division walldividing the upper part of the furnace chamber 44 from the downward gaspass 46. The bifurcations 96 might also be regarded as Y-connectionswith each of the tubes 98 being joined by such a Y-connection with twoof the tubes such as 104 and 94. Above the level of the reheater,generally indicated at 100, these tubes are parts of the refractorycovered groups of tubes 102 spaced across the gas flow from the top ofthe furnace chamber 44 to the top of the gas pass 46. These refractorycovered groups of tubes 102 are constructed and arranged so as tominimize heat absorption by the tubes at the outlet of the, furnacechamber 44. This promotes higher furnace gas temperatures at thepositions wherein the furnace gases turn downwardly at the top of thedownflow gas pass and contact the banks of tubes of the reheater and theprimary superheater. The other tubes in these groups 102 lead frombifurcations similar to 96. The upper legs 104 of these bifurcationscontinue downwardly through the tubes of the platens 106 and 108 whichextend vertically through the lower part of the furnace chamber 44. Atthe lower ends of these platens, the component tubes extend through theinclined wall including tube sections 86 and 88 to direct connectionwith the drum 36 as clearly indicated in the drawing.

The front wall 40 of the furnace chamber 44 and the forward portions ofits side walls 66 and 68 include large diameter risers such as 110, 111and 112 of the wall cooling system for the cyclone furnace. These largediameter risers are connected to the left portions of side wall headers62, these portions being separated from the re-.

mainders of the headers by diaphragms 63. Some of these risers, asindicated by the numeral in Fig. l, have sections such as 114 extendingupwardly from an upper cyclone header 116 which is fed by substantiallysemi-circular tubes extending around the cyclone to a lower header 118,the latter being in communication by tubular connectors with the drum36. All of the above indicated risers, steam generating tubes or walltubes are pendently supported from horizontally disposed steelwork suchas 121 which is, in turn, supported by columns 122 and 124. Some of thependent supports from the steelwork to the tubes are connected withhangers as indicated at 126128.' Many of the tubes are directlysupported from the drum 54 which has the pendent supports 130 securedupon elements 132 of the steelwork.

- The fluid circulation system of the illustrative installar tion.includes a series of downcomers having their lower ends directlyconnected to the drum 3.6 and their upper ends directly connected to thewater space of the drum 54; These downcorners are disposed and securedin hollow square arrangement such as indicated at 138 in the upperpartof Fig. 1, covered by heat insulating material. Steam flows from thesteam space of the drum 54 through tubular connectors 140 to the uprightconduit 142 and through that conduit to the inlet header 144 of theprimary superheater including the bank of return bend and seriesconnected tubes 146. From these tubes it flows into the intermediateheader 148 and thence upwardly through other banks of return bend.tubeswhich are formed in a manner similarto those of the reheater 100,the reheater and the superheater, above thebank of tubes 146, beingseparated by metallic division wall 150 (see Fig. 2). From the outletheader 152 of the primary superheater steam fiow through a conduit 154to the inlet header 156 of the secondary superheater which includes aplurality of upright platens formed by series connected tubes anddistributed on relatively wide spacings across the gas flow in the upperpart of the furnace chamber 44.

Water spray heads are associated with a part of the conduit 154 toconstitute an attemperator. From the header 156, the steamflows throughdownwardly diverging rows of tubes 158 and 160. Tubes 158 extenddownwardly through the roof of the furnace chamber 44, and thence acrossthe gas outlet of the furnace chamber 44 and then along the walldividing the upper part of that furnace chamber from the downfiow gaspass 46. At the position 162 intermediate the height of this wall, thetubes 158 are fanned out to upright platen formation, forming parts 164of superheater platens. These are the rearward parts of platens 166which are indicated in Fig. 2. At the lower end of these parts of theupright platen tubes, these tubes are bent to the left as indicated inFig. 1, and form the lower parts of inclined platens having their lowerends directly connected to the header 168. This header has the lowerends of the superheater tubes 160 also connected thereto.

The superheat er inlet tubes 158 enter the header 168 at the lowermostright hand position. With respect to the other tubes connected to thatheader, the superheater inlet tubes 160 enter the header 168 at aposition to the extreme left. Steam flows out of the header 168 throughtwo groups of tubes the lower ends of which are indicated 'at 170 and172. These tubes fan out into platen formations where, they crossbetween thesteam generating tubes disposed along the wall 40. 'It willbe understood that there are several groupsof these tubes along thelength.

of the header 168, and each pair of groups constitutes at least, a partof a platen of tubes extending at a horizontal inclination and in platenformation as indicated at 174 in Fig. 1. They continue toward the otherside of the furnace chamber 44 and then bend upwardly in platenformation to constitute such platens as those indicated at 166 in Fig.2. This figure shows a series of parallel platens disposed across thefurnace chamber 44. Every pas -betweenwall tub s along he ldfl at the poitian 190. From hi p sit o an wa t r gh these tubes form parts ofhorizontally inclined platens 208. At; the right hand end of thesehorizontally inclined parts, the tubes are bent to extend verticallythrough the roof of the furnace chamber 44, above which the tubes havereturn bends 192. From these return bends the tubes continue downwardlyin platen alignment with adjacent upflow tubes to the position 194 atwhich they are bent to the left to continue in horizontally inclinedplaten formation through wall tubes along the walls 40 and to points ofconnection 196 with the header 198. The upright platen parts formedby'the tubes just described are augmented by other tubes200, extendingfrom the-header 198 between the wall tubes and to a position of platenalignment with the tubes conducting the upflow steam .from the. header186 to those conducting the downfiow of steam to the header 198. Theupright parts of the tubes 200-are indicated at] 202. They extendthrough the roof of the installation above which they have return bends204. From these return bends, the tubes continue heater, or reheatsuperheater.

other platen is formed by thevertical continuations. of the tubes justdescribed. The tubes of these platens 166 extend upwardly between theroof tubes 42 of the installation. Above the roof they haveQU-bends 167(Fig. 4) and they return in. platen formation between adjacent pairs ofroof tubes to form platens such as those indicated at 18min Fig. 2, thelatter being alternately disposed with reference to the platens 166. Thesteam then flows downwardly through the tubes ofthese platens to aposition such as that indicated at 182, Fig. 1. At this positionthetubes ofthe'platens 180 are bent to the left to form the horizontallyinclined platens 183 extending across the furnace chamber 44 and thenbetween wall tubes along the wall 40, and thence to positions 184 ofconnection to the, intermediate secondary superheater header 18.6,.vFrom thisheader steam flows through groups of tubes 188 which are fannedout in platen formation where they downwardly through the roof and havevertical portions 206 in vertical alignment with the adjoining tubes tocomplete the platens indicated at 208 in Fig. 2. These are uniformlydistributed across the width of the upper part of the furnace chamber 44as clearly indicated in the drawings. Steam flows from the lastmentioned tubes 206 through'their horizontally inclined parts 210between adjacent wall tubes along wall 40 to points of connection withthe header 212. The flow continues from this header through the conduit214 to a point of use.

7 In the illustrative installation, the steam flows from the conduit'214to a multiple turbine installation from a part of which the expandedsteam flows at lower pressure and lower temperature into the inletheader 216 of the re- From this header, the steam flows through banksoftubes 218,221 of series connected return bend tubes vertically andhorizontally spaced and disposed'across the downward flow of gases; inthe downpass 46. From the tubes of the last of these banks of tubes,221, steam flows into the outlet header; 224 and thence to a succeedingcomponent of the turbine installation.

The drawings further disclose an air heater 230 inf ,cluding a. bank 232of horizontally spaced vertically disthrough from the dampered gasoutlet 78 at the lower end of the downfiow gas pass 46. Air to be heatedflows externally and recurrently transversely of these tubes and thencethrough appropriate ductwork to the air inlets of the cyclone furnace16. I

The structure near the base of the air heater includesthe breeching 236and the dust hopper 238 which unite to form an enclosed passage for thefurnace gases from the lower part of the gas pass 46 to the inlets ofthe air heater tubes 232.

For the purpose of controlling the superheat, particularly of a wideload range, the illustrative installation includes a recirculated gassystem including means for recirculating a portion of the furnace gasesfrom the recirculated gas inlet 24%, just below the air heater, throughthe external duct 242 to the ductwork 244 leading to the 111161; of thefan 246. The gas discharge of this fan is response to one or morevariables such as final superheat temperature, steam flow, and firingrate of the fuel burnmg means, to effect a uniform optimum degree ofsuper-- heat over a wide load range, extending from a value near fullload to a fraction thereof. The illustrative control of superheat bycontrol of the rate of fiue gas recirculation to maintain apredetermined superheat over a wide.

load range, further is affected by the readjustment between the fiow offurnace gases over the superheater and the reheater in their differentportions of thedownfiow pass 46. This readjustment is effected bycontrol of the dampers positioned at the lower end, or outlet, of thatpart of the downflow pass containing the reheater 100.

For heat insulation purposes, the headers, circulators, and parts oftheir steam generating and steam conducting tubes disposed above theroof of the installation are disposed within an enclosure including asuperposed cover 256, a front wall 258, and corresponding side walls. aThe rear walls of this enclosure is formed by the upper extens'ion ofthewall 72.

To obtain the optimum high degree of superheat by the illustrativeinstallation, the superheater platens are disposed in a gas zone whichhas a temperature higher than the slagging temperature of the fuel, andthese platens are disposed at a wide spacing to inhibit any slagbridging. In this respect it is to be noted that the groups of platens174 and 183 are on wide spacings, with their spacing about double thespacing of the superposed groups of platens 208 and 210. Also, thelowermost tubes of the platens 174 are formed by parts of the tubes 158extending downwardly from the inlet header 156 of the secondarysuperheater. Therefore, these lowermost tubes of the platens 174 areconducting steam at a temperature lower than the temperature of thesteam in the tubes of the superposed platens, and at a temperature lowerthan the temperature in the remaining parts of the platens 174. Both ofthese conditions, as to spacing the tubes and as to the temperature ofthe fiuid within the tubes, promote cooling of the gases and theirsuspended solids to temperatures at which the latter will not exist insuch sticky condition as will cause them to stick to the tubes andaccumulate thereon. After the temperature of the gases are lowered bywidely spaced platens 174 and 183, the gases contact the platens 208 and210 which are arranged with narrower spacing, about one-half the spacingof the lowermost sets of platens. The spaced platens of the installationeffect a high rate of heat absorption. Ninety percent or more of thetotal heat absorbed is transmitted by radiation and the remainder byconvection.

The platens permit a greater area of heat absorbing surface than couldbe economically arranged as a radiant superheater consisting of furnacewall tubes or other furnace boundary surface tubes. Furthermore, theexposure of the tubes of the secondary superheater to uniform heateffects on all sides -of the tubes results in the most effective use ofthe expensive steel alloys required in superheaters for attaining thehigh temperatures involved. By the application of heat to all sides ofthe superheater tubes, the temperatures throughout the peripheries ofthe tubes are substantially the same, and metal stresses due totemperature differentials in the tubes are thereby minimized.

Furthermore, the dog leg arrangement of the tubes forming the platens ofthe superheater permits effective support at the upper ends of theplatens. It. also permits draining of the superheater to the lower endjunction header outside of the furnace wall tubes. This arrangement alsoelimnates substantial metal stresses which would occur in otherarrangements. This is accomplished by the angular arrangement of theindividual superheater tubes with the intermediate or dog leg partsbeing relatively free to move as a result of temperature changes withoutimposing substantial stresses upon the supports for the tubes.

Among the characteristics of the illustrative installation is the factthat there is no bank of convection heated tubes in front of the platensof tubes of the secondary superheater. The latter are disposed in a zonewhich, in

many cases, would be otherwise a part of the furnace.

This part of the furnace, 'or furnace chamber, is not a combustionchamber, because the combustion is complete before the zone of thesuperheater platens is reached. The zone of these platens is,'however, azone in which ash particles are in a plastic condition as a result ofthe high temperatures.-

It is to be understood that terms and expressions used herein are usedby way of example, and not of limitation. The installation is shown anddescribed as a steam gener-J ating and steam superheating installation,but in this case the term steam is to be taken as an example ofanelastic fluid capable of the same generation and treatment for power orother industrial uses. Where the term water is used, it is to be takenas an example of a vaporizable fluid.

Similarly, the cyclone furnace is to be taken as an example of a fuelburner or fuel burning means firing the installation at temperaturesabove the fusion temperature of the ash content of the fuel.

What is claimed is:

1. Vapor generating and heating apparatus including an elongated furnacechamber having a heating gas outlet adjacent one end thereof, means forburning a fuel in said furnace for the generation of heating gases, acan vection gas pass opening from the heating gas outlet of saidfurnace, means dividing said convection gas pass into parallel gaspasses, the first of said parallel convection gas passes having vaporsuperheating tubes therein disposed in heat exchange relationship withthe gases passing therethrough, the second of said parallel convectiongas passes having vapor reheating tubes therein disposed in heatexchange relationship with the gases passing therethrough, and a vaporsuperheater disposed in heat exchange relationship with the heatinggases in both of said parallel gas passes and downstream in a gas flowsense of said first mentioned superheater and said reheater, said lastnamed superheater being connected for series flow of vapor to said firstnamed vapor superheating tubes.

2. Vapor generating and heating apparatus including an elongated furnacechamber having a heating gas outlet adjacent one end thereof, means forburning a fuel in said furnace for the generation of heating gases, aconvection gas pass opening from the heating gas outlet of said furnace,means dividing said convection gas pass into parallel gas passes, thefirst of said parallel convection gas passes having vapor superheatingtubes therein disposed in heat exchange relationship with the gasespassing therethrough, the second of said parallel convection gas passeshaving vapor reheating tubes therein disposed in heat exchangerelationship with the gases passing therethrough, a vapor superheaterdisposed in heat exchange relationship with the heating gases in both ofsaid parallel gas passes and downstream in a gas flow sense of saidfirst mentioned superheater and said reheater, said last namedsuperheater being connected for series flow of vapor to said first namedvapor superheating tubes, and means for proportioning the flow ofheating gases through said parallel gas passes.

3. Vapor generating and heating apparatus including an elongated furnacechamber having a heating gas outlet adjacent one end thereof, radiantsuperheater means including tube platens positioned in said furnacechamber, means for burning a fuel in said furnace for the generation ofheating gases, a convection gas pass opening from the heating gas outletof said furnace, means dividing said convection gas pass into parallelgas passes, the first of said parallel convection gas passes havingvapor superheating tubes therein disposed in heat exchange relationshipwith the gases passing therethrough, the second of said parallelconvection gas passes having vapor reheating tubes therein disposed inheat exchange relationship with the gases passing therethrough, and avapor superheater disposed in heat exchange relationship with theheating gases in both of said parallel gas passes and downstream in agas flow sense of said first mentioned superheater and said reheater,said last named superheater being connected for series flow of vapor tosaid first named vapor superheating tubes.

s '1 Vapor generating and helating apparatus-including an elongatedfurnace chamber having a heating gas outlet adjacent one endthereof,means for burning a fuel in said furnace for the generation ofheatinggases, a convection gas pass opening from the heating gas outletyof saidfurnace, means dividing said convection, gas, pass into parallel gaspasses, the first of said parallel convection gas. passes having vaporsuperheating tubes therein disposed inheat exchange relationship withthe gases passing therethrough, the second of said parallel convectiongas passes having vapor reheating tubes therein disposed in heatexchangerelationship with the gases passing therethrough, a vaporsuperheater disposed in heat exchange relationship with the heatinggases in both of said parallel'gas passes anddow-nstrearn in a gas flowsense of said first mentioned superheater and said"reh'eater, said thegeneration of:heatinggases, walls defining a convection gas pass openingfrom the heating gas outlet of said furnace, baffle means dividing saidconvection gas pass into separate parallel gas passes, the first of saidparallel convection gas passes having vapor superheating tubes thereindisposed in heat exchange relationship with the gases passingtherethrough, the second of said parallel convection gas passes havingvapor reheating tubes therein disposed in heat exchange relationshipwith the gases passing therethrough, and a vapor superheater disposed inheat exchange relationship with the heatinggaces in both of saidparallel gas passes and downstream in a gas flow sense of said firstmentioned superheater and said reheater, said last named superheaterbeing connected for series flow of vapor to said first named vaporsuperheating tubes.

6. Vapor generating and heating apparatus including Walls defining anelongated furnace chamber having a heating gas outlet adjacent one endthereof, vapor generating tubes positioned in the walls of said furnacechamber, means for burning a fuel in said furnace for the generation ofheating gases, walls defining a convection gas pass opening from theheating gas outlet of said furnace, baffle means dividing saidconvection gas pass into separate parallel gas passes, the first of saidparallel convection gas passes having vapor superheating tubes thereindisposed in heat exchange relationship with the gasespassingtherethrough, the second of said parallel convection gas passeshaving vapor reheating tubes therein disposed in heat exchangerelationship with the gases passing therethrough, a vapor superheatertransversely disposed in heat exchange relationship with the heatinggases in both of said parallel gas passes and downstream in a gas flowsense of said first mentioned superheater and said reheater, said lastnamed superheater being connected for series flow of vapor to said firstnamed vapor superheating tubes, and damper means positioned downstreamof said last mentioned superheater for propor-.

tioning the flow of heating gases through said parallel gas passes.

7. Vapor generatingrand heating apparatus including walls defining anelongated furnace chamber having a heating gas outlet adjacent one endthereof, vapor generating tubes positioned in the walls of said furnacechamber, radiant superheater means including. tube platens positioned insaid furnace chamber, means for burning a fuel in said furnace for thegeneration of heatgreases ing-gases, a convection gas passopeningfronrthe -heating gas outlet of said furnace, means dividing saidconvection gas pass into parallel gas passes, the first of said parallelconvection gas passes having vapor superheating tubes therein disposedin, heat exchange relationship with the gases passing therethrough, thesecond of said parallel convection gas passes having vapor reheatingtubes therein disposed in, heat exchange relationship with the gasespassing therethrough, a vapor superheater disposed in heat exchangerelationship with the heating gases in both of said parallel gas passesand downstreamin a gas flow sense of said first mentioned superheaterandsaid reheater, and means connecting said convection superheaters inseries flow relationship from said last named superheater to said firstnamed superheating tubes and thence with said radiant superheater.

8. Vapor generating and heating apparatus including walls defining anelongated furnace chamber having a heating gas outlet adjacent one endthereof,vapor gencrating tubes in thewalls of said furnace chamber,means for burning a fuel in said furnace for the generation of heatinggases, walls defining a convection gas pass opening from the heating gasoutlet of said furnace, 'vapor generating tubes positioned in the wallsof said convectiongas pass refractory means covering the vaporgenerating tubes of said convection gas pass to reduce the heat fiowtosaid ,vapor generating tubes, means dividing said convection gas passinto parallel gas passes, the first of said parallel convection gaspasses having vapor superheating tubes therein disposed in heat exchangerelationship with the gases passing therethrough, the second of saidparallel convection gas passes having vapor reheating tubes thereindisposed in heat exchange relationship with the gases passingtherethrough, a vapor superheater disposed in heat exchange relationshipwith the heating gases in both of said parallel gas passes anddownstream in a gas flow sense of said first mentioned superheater andsaid reheater, said last named superheater being connected for seriesflow of vapor to said first named vapor superheating tubes, andmeans forregulating the heating effect of the gases passing through each of saidparallel gas passes including means for recirculating heating gases froma position downstream of said last named vapor superheater to saidfurnace chamber.

9. In a steam generating and superheating unit, the

,combination with means for generating steam by fuel combustion, ofwalls defining parallel separate convection gas passes constructed andarranged to receive heating gases from said steam generating means,steam superheating means positioned in one of said parallel gas passes,steam reheating means positioned in the other of said parallel gaspasses, steam superheating means positioned downstream in a gas flowsense of said steam superheating and reheating means and in heatexchange contact with the heating gases passing through each of saidparallel gas passes, said last named superheating means being connectedfor series flow to said first named steam superheating means, and meansfor proportioning the flow of gases through said parallel gas passes.

10. In a steam generating and steam heating unit, the combination withmeans for generating steam by fuel combustion, of walls defining aconvection gas pass constructed and arranged to receive heating gasesfrom said steam generating means, baffle means dividing said convectiongas pass into parallel gas fiow passages, steam superheating meanspositioned in one of said parallel gas flow passages, steam reheatingmeans positioned in the other of said parallel gas flow passages, steamsuperheating means positioned downstream in a gas flow sense of saidsteam superheating and reheating means and in heat exchange contact withthe heating gases passing through each of said parallel gas flowpassages, said last named superheating means being connected for seriesflow to said first named steam superheating means, and damper meanspositioned adjacent said last named steam superheating means forregulating the flow of gases through each of said parallel gas flowpassages.

' 11, In a steam generating and steam heating unit, the combination withmeans for generating steam by fuel combustion, of walls defining aconvection gas pass constructed and arranged to receive heating gasesfrom said steam generating means, bafile means dividing said convectiongas pass into parallel gas flow passages, steam superheating meanspositioned in one of said parallel gas flow passages, steam reheatingmeans positioned in the other of said parallel gas flow passages, steamsuperheating means positioned downstream in a gas fiow sense of saidsteam'superheating and reheating means and in heat exchange contact withthe heating gases passing through each of said parallel gas flowpassages, said last named superheating means being connected for seriesflow to said first named steam superheating means, and means torcontrolling the temperature and volume of the gases entering saidconvection gas pass by gas recirculation, and means for proportioningthe flow of gases through said parallel gas passes.

12. In a steam generating and superheating unit, the

combination with means for generating steam by fuel combustion, of wallsdefining a convection gas pass constructed and arranged to receiveheating gases from said steam generating means, bafile means dividingsaid convection gas pass into parallel gas flow passages, steamsuperheating means positioned in one of said parallel gas 12 flowpassages, steam reheating means positioned in the other of said parallelgas flow passages, steam superheating means positioned downstream in agas flow sense of said steam superheating and reheating means and inheat exchange contact with the heating gases passing through each ofsaid parallel gas flow passages, said last named superheating meansbeing connected for series flow to said first named steam superheatingmeans, and means for regulating the heating effect of the gases enteringsaid convection gas pass by gas recirculation in response to thesuperheated steam temperature leaving said unit, and means forproportioning the flow of gases through said parallel gas passes inresponse to reheated steam temperatures.

References Cited in the file of this patent UNITED STATES PATENTS2,002,463 Bailey et a1. May 21, 1935 2,064,444 Mosshart et al. Dec. 15,1936 2,091,231 Shellenberger Aug. 24, 1937 2,213,185 Armacost Sept. 3,1940 2,287,798 Hardgrove et al. June 30, 1942 2,628,598 Van Brunt Feb.17, 1953 1 FOREIGN PATENTS 23,499 Australia July 13, 1935 516,070 GreatBritain Dec. 21, 1939

